We propose a new type of experiment for studying the structure of biologically active macromolecules; a chromophore "probe" will be attached to the macromolecule and resonance Raman spectroscopy will be performed to determine the vibrational spectrum of the probe labelled biomolecule. We have previously used this technique to study the active site of liver alcohol dehydrogenase. A coenzyme competitive inhibitor, zincon, was bound to the active site as a structural "probe". The vibrational and electronic spectra of the complex were determined. The vibrational spectrum indicated direct complexation of zincon to the zinc atom at the active site. However, the electronic spectrum was not useful in diagnosing this ligand metal interaction; this is indicative of the power of the new technique for determining the chemical environment at the active site of a macromolecule. We propose to carry out resonance Raman investigations of reversibly bound probe molecules, of irreversibly bound alkylating probes, and of chemical intermediates formed during enzyme reactions. These techniques will be used to study the enzymes lactate dehydrogenase, yeast alcohol dehydrogenase, glyceraldehyde-3-phosphate dehydrogenase, and liver alcohol dehydrogenase, mitochondrial membrane preparations and acetylcholine receptor complexes from eel electroplax.